The Cummins heavyduty B5.9 natural gas engine has been in production since 1994, and was the industries’ first engine with closed-loop A/F ratio control.

Cummins also developed (1999) a propane version of this engine called the B5.9LPG. It utilizes lean combustion, closed-loop A/F ratio control, and electronic engine management technologies. Although the engine is similar to natural gas version, extensive engine development was required to modify the engine for LPG operation.
Engine performance was optimized for combustion, detonation, and lean misfire margins with
LPG versus natural gas. For example, the optimal compression ratio for LPG was 9.1:1
compared to 10.5:1 for natural gas. Development and validation for operation on LPG required
more than 10,000 laboratory test hours.15

There has been a trend in time from the early 80’s toward increased BMEP because it produces higher efficiency and ultimately reduces cost.16

On the most advanced engines, thermal efficiency is now as high as 45% at 20 bar BMEP

For any engine size, 20 bar BMEP is hard to achieve in knock and misfire free operation. Higher BMEP levels result in higher efficiency as parasitic losses are smaller in proportion to engine power. Larger bore sizes are typically more efficient due to the reduction in surface to volume ratio and resulting heat loss through the cylinder, head and piston surfaces and less (relative) opportunity for crevice fuel quenching.

Larger engines run slower than smaller bore engines with linear piston speed fairly constant across sizes. Slower speed engines also benefit from reduced friction in rotating components.

Electric efficiencies of natural gas engines range from 28% Lower Heating Value (LHV) for stoichiometric air to fuel ratio engines smaller than 100 kW
to more than 40% LHV for larger lean-burn engines (> 2 MW).17

Currently, the maintenance interval is dictated by the spark plug change interval. Market forces call for increased engine efficiency while regulations call for lower emissions on the future spark ignited natural gas engines. However, experiences indicate the use of traditional ignition systems on leaner A/F mixtures and higher charge densities requires stronger ignition spark
which in turn reduces spark plug life.18 This is a concern as it may represent a barrier to the continued trend toward higher engine efficiency.19

from chapter 4 of

http://www.fossil.energy.gov/program...bility-rpt.pdf

 

Lots of jargon in there but I don't think you intended this toward the rocket scientist types. First, is it still diesel engine? With spark plugs, I guess not. I was wondering myself if a diesel engine could be made using natural gas so we can become independent from foreign oil. If a diesel works by basically increasing pressure to increase the temperature to the point of ignition (if this is correct), couldn't that be done with natural gas?

I am very new to diesel, but it would be neat if we could further the technology and still keep the benefits, unlike the hacks at the EPA.

 

yeah i agree with you, it would not be considered a cummins if it can't burn diesel (which would be hard with spark plugs)... what i am trying to say is: are you sure it is not a 5.9 360 gasser? <- as that would make more sense

 

yes, some of the generators I work on are NG, most of the loder ones have the spark plug in em, there the same engine, cummins, detroit, whatever, just with a spark plug. But the newest ones, and larger ones for that part burn NG with no assist from spark, but there comprssion ratio is through the roof, makes normal diesel ratio look like gasoline..